1. Field of the Invention
The invention relates to medical devices for percutaneously accessing and performing therapy on body lumens and cavities and, more particularly, to methods and devices for clot or debris removal within the cardiovascular system, peripheral vasculature, or neurovasculature.
2. Description of the Related Art
Thromboembolic disorders, such as occlusive stroke, pulmonary embolism, myocardial infarct, peripheral thrombosis, cerebrovascular occlusion, atherosclerosis, and the like, affect many people. These disorders are a major cause of morbidity and mortality in the United States.
Thromboembolic events are characterized by an occlusion of a blood vessel. The occlusion can be caused by a clot or thrombus, which can be viscoelastic (jelly-like) and is comprised of platelets, fibrinogen, and other clotting proteins. The occlusion can also be more rigid material such as plaque, which has broken off from a vessel wall upstream of the site of the occlusion.
When a clot occludes an artery, tissue ischemia (lack of oxygen and nutrient delivery to the tissue) can develop. The ischemia can progress to tissue infarction (cell death) if the occlusion persists. Infarction does not develop or is greatly limited if the flow of blood is reestablished rapidly. Failure to re-establish blood flow can lead to the loss of limb, angina pectoris, myocardial infarction, stroke, compromised cognitive or neural function, or even death.
Occlusion of the venous circulation by thrombi leads to blood stasis, which can cause numerous problems. The majority of pulmonary embolisms are caused by emboli that originate in the peripheral venous system although occlusions of the cerebrovasculature occur in millions of Americans yearly, often with catastrophic results. Reestablishing blood flow and removal of the thrombus or occlusion is critically important for the well being of these patients.
There are many existing techniques employed to reestablish blood flow in an occluded vessel. One common surgical technique, an embolectomy, involves incising a blood vessel and introducing a balloon-tipped device, such as the Fogarty® catheter, to the location of the occlusion. The balloon is then inflated at a point beyond the clot and used to translate the obstructing material back to the point of incision. The surgeon can, then, remove the obstructive material. While such surgical techniques have been useful, exposing a patient to surgery may be traumatic and best avoided when possible. Additionally, the use of a Fogarty catheter is problematic because of the great risk of damaging the interior lining of the vessel as the catheter is being withdrawn.
Percutaneous methods are also utilized for reestablishing blood flow. A common percutaneous technique is referred to as balloon angioplasty where a balloon-tipped catheter is introduced to a blood vessel, typically through an introducing catheter. The balloon-tipped catheter is then advanced to the point of the occlusion and inflated in order to dilate the stenosis. Balloon angioplasty is appropriate for treating vessel stenosis but is not effective for treating acute thromboemboli.
Another technique is thrombolysis wherein a thrombolytic agent (e.g., streptokinase, urokinase, tissue plasminogen activator (TPA) is administered systemically or locally through a catheter. Unfortunately, thrombolysis typically takes hours to days to be successful. Additionally, thrombolytic agents can sometimes cause hemorrhage and in many be contraindicated in certain patients.
U.S. Pat. Nos. 4,706,671 (Weinrib) and 5,011,488 (Ginsburg) both describe the use of percutaneously inserted catheter-based devices for removal of thromboembolic material. In particular, U.S. Pat. No. 4,706,671 teaches the use of a hollow flexible elastomeric material to form the shape of the coiled section. The coiled section is hollow to allow for the insertion of a liquid into the hollow center such that the coils become stiff. U.S. Pat. No. 5,011,488 teaches the use of a coiled section that is fixed on both the proximal and distal ends such that the operator of the device can change the shape and size of the coils. In addition, U.S. Pat. Nos. 5,895,398 (Wensel et al.) and 6,530,935 (Wensel et al.) describe a clot and foreign body removal device which comprises a catheter having at least one lumen and a clot capture coil that is connected to an insertion mandrel. In one embodiment, the clot capture coil is made out of a solid elastic or superelastic material which has shape memory, preferably nitinol. The elasticity or superelasticity of the coil allows it to be deformed within the catheter and to then reform its original coil configuration when the coil is moved outside of the catheter lumen. In another embodiment the coil is a biphasic coil which changes shape upon heating or passing an electric current. In operation, the catheter is advanced through the clot and the mandrel with the clot capture coil attached is advanced through the catheter and out of its distal end. The superelastic or biphasic coil then assumes its coiled configuration. Once the coil configuration has been established, the coil can be used to ensnare and corkscrew a clot in a vessel. A clot is extracted from the vessel by moving the clot capture coil and catheter proximally until the clot can be removed or released into a different vessel that does not perfuse a critical organ. Foreign bodies are similarly captured by deploying the coil distal to the foreign body and moving the clot capture coil proximally until the foreign body is trapped within the coil. By removing the device from the body, the foreign material is also removed.
Foreign bodies introduced into the circulation can be fragments of catheters, pacemaker electrodes, guide wires, and erroneously placed embolic material such as thrombogenic coils. The available retrieval devices for the removal of foreign bodies include devices which form a loop that can ensnare the foreign material by decreasing the size of the diameter of the loop around the foreign body. The use of such removal devices can be difficult in at least some cases and sometimes unsuccessful.
Thus, there exists a need for the development of a device that can be easily deployed into the circulatory system for the removal of various materials including viscoelastic clots and foreign bodies. There is also a need for a device that can be used as a temporary arterial or venous filter to capture and remove thromboemboli formed during endovascular procedures.
U.S. Pat. No. 5,102,415 (Guenther et al.) describes a system for removing obstructions from blood vessels comprising balloon catheter and another catheter having an expandable tip, which receives the obstruction. The balloon catheter is passed through the obstruction while the balloon is deflated. The balloon is then inflated and the tip of the catheter is expanded. The balloon is then moved proximally so that the obstruction is pulled into the expanded tip of the catheter. A problem with the system of U.S. Pat. No. 5,102,415 is that the interaction between the balloon catheter and the leading edge of the catheter may tend to shear off portions of the obstruction. This can cause obvious problems when working in sensitive vascular areas since pieces of the obstruction can migrate and cause further obstruction with adverse ischemic consequences.
A need, therefore, remains for improved obstructive matter removal technology, which allows a device to be percutaneously or surgically introduced, transluminally advanced to a target body lumen and across or through the obstructive matter (e.g., a thrombus), thereafter expanded and then retracted and removed along with the obstructive matter.